1. Field of the Invention
The present invention relates to the field of semiconductor integrated circuit manufacturing and more specifically to medium temperature deposition and high temperature deposition of silicon oxide films and methods of fabrication of these oxide films.
2. Discussion of Related Art
Chemical vapor deposited (CVD) SiO2 films and their binary and ternary silicates (generally referred to as oxide films) have wide use in fabrication of integrated circuits such as microprocessors and memories. These films are used as insulation between polysilicon and metal layers, between metal layers in multilevel metal systems, as diffusion sources, as diffusion and implantation masks, as spacers, and as final passivation layers. Acceptable deposited oxide film processes provide uniform thickness and composition, low particulate and chemical contamination, good adhesion to the substrate, and high throughput for manufacturing.
These films are formed using well known techniques such as CVD. Low-pressure chemical vapor deposition (LPCVD) is a special case of a CVD process, typically used for front end of line (FEOL) dielectric film deposition. In a CVD process, a given composition and flow rate of reactant gases and diluent carrier gases are introduced into a reaction chamber. The gas species move to a substrate and the reactants are adsorbed on the substrate. The atoms undergo migration and film-forming chemical reactions and a film (e.g., silicon oxide) is deposited on the substrate. The gaseous byproducts of the reaction and removed from the reaction chamber. Energy to drive the reactions can be supplied by several methods, e.g. thermal, light and radio frequency, catalysis, or plasma. A conventional CVD system typically contain gas sources, gas feed lines, mass-flow controllers, a reaction chamber, a method for heating substrates onto which the film is to be deposited, and temperature sensors. A conventional LPCVD system is similar to the CVD system except that temperature is the primary driver for the reaction of source gases.
A state of the art system for forming a medium temperature deposition oxide film (MTO) and a high temperature deposition oxide film (HTO) on a substrate utilizes a batch type LPCVD system which is depicted in FIG. 1A. This figure illustrates a batch type LPCVD system 100 which is a hot wall furnace system including a three-zone resistance furnace 112, a quartz reactor tube 102, a gas inlet 104, a pressure sensor 106, and a wafer boat 108. A plurality of silicon wafers 110 are vertically positioned upon the wafer boat 108 for deposition. The wafers are radiantly heated by resistive heating coils surrounding the tube 102. Reactant gases are metered into one end of the tube 102 (gas inlet 104) using a mass flow controller. Reaction by-products are pumped out the other end of the tube 102 (e.g., via an exhaust pump).
The state of the art system suffers a disadvantage called xe2x80x9cdepletion effects.xe2x80x9d Depletion effects reduce gas phase concentrations as reactants are consumed by reactions on wafer surfaces. As such, wafers near the inlet 104 are exposed to higher concentrations of reactant gases. Deposition rates are thus greater for wafers placed near the inlet 104. As a result, uniform thickness is difficult to obtain for the wafers in a batch and from batch to batch.
A process for forming a silicon oxide film, or a silicon oxynitride film, is described. The film is grown by a thermal low-pressure chemical vapor deposition process. The process can be performed in a single wafer cold wall reactor wherein a silicon source gas and an oxidation source gas are decomposed using a thermal energy source in a deposition chamber to form the film. The film is formed with a total pressure between 50 to 350 Torr and with a flow ratio between 1:50 to 1:10000, silicon source gas flow to oxidation source gas flow, respectively. The process enables forming of films having thickness less than 100 xc3x85 and greater than 1000 xc3x85 with a deposition rate between 20 xc3x85 per minute to 2000 xc3x85 per minute.